The present invention relates generally to center of gravity location and, more particularly, to a system for estimating, in real time, vehicle conditions relating to loading/unloading for determination of vehicle mass, pitch moment of inertia, and center of gravity location.
Current systems estimate the vehicle center of gravity and merely assume the best weight of the vehicle distributed over the four wheels. On line knowledge of changes in vehicle mass, inertia, and change in center of gravity location can be used to apportion braking effort from front to rear, optimize active suspension heights and stiffnesses, adjust steering angles in a four wheel steered vehicle, and optimize traction control action.
For example, U.S. Pat. No. 4,603,921, issued to Liggett, discloses a brake proportioning system for a vehicle which is responsive to the presence or absence of loads exceeding a threshold at various locations in the vehicle, such as passenger or cargo-carrying locations. Load presence sensor switches, a signal processing system such as an onboard computer, and an electrically controllable brake proportioning valve respond to the presence of weight in a vehicle. The ratio of rear-to-front braking effort is controlled by the proportioning valve so that the ratio increases as the number of passengers and cargo-load presences increases. Both the weight and the location of the loads influences the brake proportioning ratio.
One method of determining the load on a vehicle is disclosed in U.S. Pat. No. 4,691,792, issued to Shintani. The Shintani reference discloses a method and apparatus for measuring the net weight of a load on a vehicle. The method for measuring the weight of a load includes the steps of detecting axial force applied to each suspension cylinder mounted between the vehicle body frame and the axles, and then compensating for or correcting the detected axial force in accord with respective mounting angles of links mounted in the axle and the inclination angle of the vehicle body.
In U.S. Pat. No. 4,110,605, issued to Miller, a method for computing the gross weight and center of gravity for an aircraft instrumentation and control system is disclosed. The computations are made by measuring longitudinal axis and normal axis acceleration components in conjunction with air data parameters, pressure ratios or fan speeds of the engines and the positions of the flap-slat and horizontal stabilizer aerodynamic control surfaces. However, for an aircraft, the center of gravity and weight are determined based on dynamic equilibrium; whereas, for a car, measurements are based on static equilibrium.
It is seen then that there is a need for a vehicle center of gravity estimator which adjusts to changes in vehicle parameters due to loading and unloading of fuel, passengers, and/or cargo, based on static equilibrium.